ccckmit · August 29, 2015 14:16 · Mar 2, 2015 · Mar 2, 2015
diff --git a/gistfile1.txt → gistfile1.js b/gistfile1.txt → gistfile1.js
diff --git a/gistfile1.txt b/gistfile1.txt
@@ -0,0 +1,122 @@
+// 原始程式來源: http://practicalcryptography.com/ciphers/enigma-cipher/ 網頁內的 javascript 程式碼
+
+var c = console;
+
+var plaintext = 'ABCDEF';
+c.log('>> plaintext2 : '+plaintext);
+var ciphertext = Encrypt(plaintext, 'AAA', 'AAA', '123', 'POMLIUKJNHYTGBVFREDC');
+c.log('>> ciphertext : '+ciphertext);
+var plaintext2  = Encrypt(ciphertext, 'AAA', 'AAA', '123', 'POMLIUKJNHYTGBVFREDC');
+c.log('>> plaintext2 : '+plaintext);
+
+
+function Encrypt(plaintext, keysettings, ringsettings, rotorsettings, plugboardsettings) {
+    c.log('plaintext='+plaintext);
+    c.log('keysetting='+keysettings);
+    c.log('ringsetting='+ringsettings);
+    c.log('plugboardsettings='+plugboardsettings+' len='+plugboardsettings.length);
+    c.log('rotorsettings='+rotorsettings);
+    // do some error checking
+    if(plaintext.length < 1){ c.log("please enter some plaintext (letters and numbers only)"); return; }    
+    if(keysettings.length != 3){ c.log("Key settings must consist of 3 uppercase characters."); return; }
+    if(ringsettings.length != 3){ c.log("Ring settings must consist of 3 uppercase characters."); return; }
+    if(plugboardsettings.length > 26){ c.log("There cannot be more than 13 pairs in the plugboard settings."); return; }
+    if(plugboardsettings.length % 2 != 0){ c.log("There must be an even number of characters in the plugboard settings."); return; }
+    if(rotorsettings.length != 3){ c.log("Rotor settings must consist of 3 numbers 1-9."); return; }
+
+    // interpret the rotor settings (strings 1-8 to int 0-7)
+    var rotors = rotorsettings.split("");
+    rotors[0]=rotors[0].valueOf()-1;rotors[1]=rotors[1].valueOf()-1;rotors[2]=rotors[2].valueOf()-1; 
+
+    // parse plugboard settings, store as a simple substitution key
+    var plugboard = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+    var parr = plugboard.split("");
+    for(i=0,j=1;i<plugboardsettings.length;i+=2,j+=2){
+	    ichar = plugboard.indexOf(plugboardsettings.charAt(i));
+	    jchar = plugboard.indexOf(plugboardsettings.charAt(j));
+	    temp = parr[jchar]; parr[jchar]=parr[ichar]; parr[ichar]=temp;
+    }
+    plugboard = parr.join("");
+
+    // interpret key and ring settings (convert from letters to numbers 0-25)
+    key=keysettings.split("");
+    key[0]=code(key[0]); key[1]=code(key[1]); key[2]=code(key[2]);
+    ring=ringsettings.split("");
+    ring[0]=code(ring[0]); ring[1]=code(ring[1]); ring[2]=code(ring[2]);
+
+    // do the actual enigma enciphering
+    ciphertext = "";   
+    for(i=0; i < plaintext.length; i++){
+        ch=plaintext.charAt(i);
+
+        // if the current character is not a letter, pass it through unchanged
+        if(!ch.match(/[A-Z]/)){
+            ciphertext = ciphertext + ch;
+        }else{
+            key=increment_settings(key,rotors);
+            ciphertext = ciphertext + enigma(ch,key,rotors,ring,plugboard);
+        }
+    }
+    c.log('ciphertext='+ciphertext);
+    return ciphertext;
+}
+
+function enigma(ch,key,rotors,ring,plugboard){
+	// apply plugboard transformation
+	ch = simplesub(ch,plugboard);
+	// apply rotor transformations from right to left
+	ch = rotor(ch,rotors[2],key[2]-ring[2]);
+	ch = rotor(ch,rotors[1],key[1]-ring[1]);
+	ch = rotor(ch,rotors[0],key[0]-ring[0]);
+	// use reflector B
+	ch = simplesub(ch,"YRUHQSLDPXNGOKMIEBFZCWVJAT");
+	// apply inverse rotor transformations from left to right
+	ch = rotor(ch,rotors[0]+8,key[0]-ring[0]);
+	ch = rotor(ch,rotors[1]+8,key[1]-ring[1]);
+	ch = rotor(ch,rotors[2]+8,key[2]-ring[2]);
+	// apply plugboard transformation again
+	ch = simplesub(ch,plugboard);
+	return ch;
+}
+
+
+function increment_settings(key,r){
+	//notch = [['Q','Q'],['E','E'],['V','V'],['J','J'],['Z','Z'],['Z','M'],['Z','M'],['Z','M']];
+	// The notch array stores the positions at which each rotor kicks over the rotor to its left
+	var notch = [[16,16],[4,4],[21,21],[9,9],[25,25],[25,12],[25,12],[25,12]];
+	if(key[1] == notch[r[1]][0] || key[1] == notch[r[1]][1]){
+        key[0] = (key[0]+1)%26;
+        key[1] = (key[1]+1)%26;
+    }    
+    if(key[2] == notch[r[2]][0] || key[2] == notch[r[2]][1]){
+        key[1] = (key[1]+1)%26;
+    }
+    key[2] = (key[2]+1)%26;   
+	  return key;
+}
+
+// perform a simple substitution cipher
+function simplesub(ch,key){
+	  return key.charAt(code(ch));
+}
+
+function rotor(ch,r,offset){
+	  // The first eight strings represent the rotor substitutions I through VIII. The second 8 are the 
+	  //  inverse transformations
+	  var key = ["EKMFLGDQVZNTOWYHXUSPAIBRCJ","AJDKSIRUXBLHWTMCQGZNPYFVOE","BDFHJLCPRTXVZNYEIWGAKMUSQO",
+               "ESOVPZJAYQUIRHXLNFTGKDCMWB","VZBRGITYUPSDNHLXAWMJQOFECK","JPGVOUMFYQBENHZRDKASXLICTW",
+               "NZJHGRCXMYSWBOUFAIVLPEKQDT","FKQHTLXOCBJSPDZRAMEWNIUYGV",
+               // inverses
+               "UWYGADFPVZBECKMTHXSLRINQOJ","AJPCZWRLFBDKOTYUQGENHXMIVS","TAGBPCSDQEUFVNZHYIXJWLRKOM",
+               "HZWVARTNLGUPXQCEJMBSKDYOIF","QCYLXWENFTZOSMVJUDKGIARPHB","SKXQLHCNWARVGMEBJPTYFDZUIO",
+               "QMGYVPEDRCWTIANUXFKZOSLHJB","QJINSAYDVKBFRUHMCPLEWZTGXO"];
+     // the following code looks a bit horrible, but it is essentially just doing a simple substitution
+     //  taking into account 16 possible keys (8 rotors and their inverses) and the offset (which is calculated
+     //  from the indicator and ring settings). The offset essentially shifts the rotor key to the left or right
+     var chcode = (code(ch)+26+offset)%26;
+     var mapch = (code( key[r].charAt(chcode) ) +26-offset)%26 +65;
+     return String.fromCharCode(mapch);
+}
+
+// return the number 0-25 given a letter [A-Za-z]
+function code(ch){return ch.toUpperCase().charCodeAt(0) - 65;}